HIERO is not a hieroglyphic text editor. It must be considered as a help to the transliteration of hieroglyphs. Its principle is simple and WYSIWIG: on one side you have a papyrus and of the other one hieroglyphs. You just have "to drag" or to copy hieroglyphs to drop them on the papyrus; can be in the style of a scribe registering hieroglyphs on its papyrus...
You will so obtain information on the so established sequence (transliteration, grammatical structure, list of the Gardiner codes, the phonetic reading).